Cloud computing services such as, for example, infrastructure-as-a-service (IaaS), platform-as-a-service (PaaS), and software-as-a-service (SaaS), have become popular. A cloud system allows users to enjoy large-scale computing power by distributing tasks into large amount of computing nodes. The computing nodes are connected to the Internet via network switches such as, for example, edge switches, core switches, and/or core routers. If a failure occurs at one of the network switches, such a failure may propagate throughout the entire cloud system, resulting in a large-scale system failure.